In a mobile communications system, terminal device (for example user equipment (UE)) may have multiple serving cells at a same time. One serving cell is referred to as a primary cell (PCell), and a remaining serving cell is referred to as a secondary cell (SCell). The terminal device may send, in the primary cell and one or more secondary cells, a physical uplink control channel (PUCCH) to a base station (BS).
Power at which the terminal device sends the PUCCH in each cell is controlled by the base station. In the prior art, the base station sends, to the terminal device by adding a command to common search space of each cell, the command for instructing the terminal device to adjust PUCCH transmit power in each cell. In this case, a quantity of serving cells in which the terminal device can send the PUCCH is relatively large, and common search space is also relatively large. Therefore, when the terminal device detects information sent by the base station to the terminal device, common search space that the terminal device needs to detect is relatively large, that is, a quantity of blind detection is relatively large.